code: def _remove_constant_columns(X: np.ndarray) -> np.ndarray:
      X = shape_into_2d(X)
      return X[
          :,
          [np.unique(X[:, i]).shape[0] > 1 for i in range(X.shape[1])],
      ]
  
file_path: dowhy/dowhy/gcm/independence_test/kernel.py
imports: from typing import Callable, List, Optional, Union
  import numpy
  import scipy
  from causallearn.utils.KCI.KCI import KCI_CInd, KCI_UInd
  from joblib import Parallel, delayed
  from sklearn.preprocessing import scale
  import dowhy.gcm.config
  from dowhy.gcm.independence_test.kernel_operation import approximate_rbf_kernel_features
  from dowhy.gcm.stats import quantile_based_fwer
  from dowhy.gcm.util.general import auto_apply_encoders, auto_fit_encoders, set_random_seed, shape_into_2d
label_desc: Use image node_id 8 for calling a global function with example usage: _remove_constant_columns(X) and returns: X